I can't remember exactly what age I started giving myself enemas. It could not have been before I was 10 because I started after we moved into our new house and I was 10 and in fifth grade. I know for sure that I gave myself enemas after walking home from school starting in the seventh grade and that would have put me at 12 years old. It is possible I started at age 11 because my dad was away from home a lot and it seemed the bag showed up in the shower after he started to date a certain woman when I was 11 years old. Anyway, sometime in the time frame of when I was 11-12 years old I figured out what to do with the bag and nozzle.
We had three bathrooms in the house. One was a utility bathroom (sink and toilet) in the basement...a bathroom I could use to when I took an enema outside or in the basement. The pipes for the main floor of the house were exposed and made a great place to hang an enema bag. The main bathroom was a full bath with toilet, tub and sink. The third bathroom was what they termed a three-quarter bath with a toilet, sink, and built in shower off the master bedroom. My dad preferred that we took showers in that bathroom rather than the tub in the main bath.
It was a two quart, open top, Faultless red rubber bag with a screw on nozzle (usually the multi-port curved douche nozzle). The bag hung on the shower rod in the bathroom off the master bedroom. I used an anodized aluminum 16 ounce cup to fill the bag from the shower nozzle and it took 4 cups to fill the bag. I could take a full bag from the very start. Loved to feel the warm water flowing into me, holding it for a few minutes and then discharging it in the shower to wash down the drain. Then the next bag, and the next. Usually I would take two to four bags while taking a shower.
Over a period of weeks, I gradually increased the volume I held by the number of cups I added to the bag. I eventually got myself up to eight 16-ounce cups. I also increased my ability to hold the enema for longer periods of time before expelling. I tried to work myself up to ten 16-ounce cups (5 quarts) and could reach the volume occasionally, but it was mostly 4-4.5 quarts at most with two-four enema filling and expelling cycles. No additives to the water, though I did like to experiment with water temperature. I took most of the enemas standing up, though I did like to lay myself over the edge of the shower with the tube up my ass and the water flowing as I used the shower tiles to stroke myself to a nice orgasm (once I had figured out how to do that and that I liked it very much).
When I was in my 30's, I got back into enemas for a while. Liked the enemas of 3-4 quarts but had only a two quart bag and it was a combination bag that doubled as a hot water bottle as well. So, that required multiple fillings. I liked really fast fills and used really long hose lengths to hang the bag quite high to accomplish this (though I never used the straight enema pipe/nozzle, always the douche nozzle). I could hang the bag from the balcony from my bedroom overlooking my living room with a nominal height from the bag to the first floor of more than 13 feet. My back porch deck and yard was very private and I could give myself enemas outside, night and day (though if I hung my bag from my deck's railing and walked out to my ground level sun deck or my hammock in the daytime with the nozzle inserted, my neighbor could have seen me from his second floor spare bedrooms).
Now, 50 years later, I can still take that much liquid volume (and sometimes more) though my toys are more sophisticated. And there are certain enema solutions that I like to play with that I didn't play with earlier.